On one hand, it raised the bar. Tamil audiences, exposed to the visual effects of Marvel and the pacing of Mission Impossible through these downloads, began to expect similar quality from local productions. The "mass" elements of Hollywood—slow-motion walks, massive explosions—were absorbed into Kollywood's DNA.
Official platforms now provide high-quality Tamil dubbing with the option for offline downloads via their mobile apps: Disney+ Hotstar english movies dubbed in tamil download
Is watching English films/series dubbed in your target language help? On one hand, it raised the bar
The dubbing industry in South India is now a multi-crore business. Top Tamil actors (like Ajith’s dubbing artist for Hollywood films) are lending their voices to Chris Hemsworth and Tom Cruise. You are missing nothing by sticking to legal sources—in fact, you are getting the best version of the film. You are missing nothing by sticking to legal
Almost every Marvel Cinematic Universe (MCU) film—from Iron Man to Guardians of the Galaxy Vol. 3 —is available in Tamil. You can download them directly to your phone via the app for offline viewing.